Passenger vehicles in today's market incorporate a power transmission that has at least three forward ratios, and quite often, six forward ratios. These power transmissions are utilized to extend the operating range of the vehicle engine by reusing the engine speed range as the gear ratio is changed. In order to make more efficient use of the engine and its speed range, it has been proposed to employ a continuously variable type transmission wherein the ratio change within the transmission is continuous over during a drive range during which the engine speed might be held constant. For example, the continuously variable transmission ratios are changed from an underdrive of four to one (4:1) to an overdrive of point four to one (0.40:1). A step change transmission utilizing this same ratio spread would require five or six ratio steps depending upon the step ratio multiplier desired between the adjacent ratios.
The continuously variable type transmissions have been suggested as single mode and dual mode type power transmissions. Mostly, the transmissions for passenger vehicles have been proposed as geared neutral type transmission arrangements wherein the ratios in the transmission can be changed from forward to reverse without the interchange of friction devices. While these types of transmissions provide a simplified control system for forward and reverse, they do have the disadvantage in that a high portion of the power is recirculated through the continuously variable unit and the gearing during the vehicle launch operation. This reduces the transmission output torque, tractive effort, and the overall efficiency of the transmission during vehicle launch.